Alton, IA has a population of 1,325 and is the 13,439th largest city in the United States. The population density is 697 per sq mi which is 1176% higher than the Iowa average and 669% higher than the national average. The median age in Alton is 37 which is approximately 4% lower than the Iowa average of 38. In Alton, 70% of the population over 15 years of age are married, 93% speak English and 7% speak Spanish. 77% of Alton residents were born in Iowa, 19% were born out of state, 0% were born outside of the United States and 3% were foreign born.